gluon-mesh-vpn-tunneldigger: tunneldigger-watchdog: remove broken restart check

The tunneldigger init script has been migrated to procd, so there is no
PID file anymore. Remove the obsolete check altogether - it shouldn't
be needed anymore, as procd will take care of crashes of tunneldigger by
itself. This fixes the watchdog resetting tunneldigger every time it runs.

Closes #2977